This invention relates to an improved seal for use on the eccentric shafts which actuate air disc brakes, wherein the seal accommodates shaft movement.
Many heavy vehicles utilize air-driven disc brakes. In a standard air-driven disc brake, an air brake actuator selectively extends a push rod to turn an actuation lever. The actuation lever drives an eccentric shaft to rotate. The shaft is mounted eccentrically within an actuation block. When the eccentric shaft turns, it forces the block towards a surface which is to be braked.
As known, the area where the actuation lever attaches to the eccentric shaft is typically outward of a braking assembly. It is desirable to seal this outer area from the inner reaction surfaces between the shaft and the block. Typically, known seals have been a relatively rigid part with resilient sealing portions for engaging against the shaft. A housing, known as a caliper, encloses the block. The seal is typically fixed to the caliper.
The use of the relatively rigid seal body has presented some problems due to practical realities in this type of brake system. In one major problem, the eccentric shaft may sometimes become skewed within the block. When this happens, the seal utilized in the prior art is not as effective, since the seal is designed based upon the assumption that the shaft will be perpendicular to an opening within the block. Thus, the prior art seal does not function as effectively if the shaft is skew, which does happen in braking applications.
When the eccentric shaft has become skew within the prior art seal, there has sometimes been deformation of the sealing area. This is, of course, undesirable.
Also from time-to-time the shaft may move axially which also makes it difficult for the seal to perform properly.